Relationships between major and trace elements during weathering processes in a sedimentary context: Implications for the nature of source rocks in Douala,Littoral Cameroon |
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| Institution: | 1. Higher Teachers Training College, University of Yaounde I, P.O. Box 47, Yaounde, Cameroon;2. Faculty of Science, University of Yaounde I, P.O. Box 812, Yaounde, Cameroon;3. Ministry of Scientific Research and Innovation, P.O. Box 1457, Yaounde, Cameroon;1. Department of Chemical Engineering, Babes-Bolyai University, 11 Arany Janos St., RO-400028 Cluj-Napoca, Romania;2. National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath St., RO-400293 Cluj-Napoca, Romania;3. Department of Geology, Babes-Bolyai University, 1 M. Kogalniceanu St., RO-400048 Cluj-Napoca, Romania;4. Department of Environmental Analysis and Engineering, Babes-Bolyai University, 30 Fantanele St., RO-400294 Cluj-Napoca, Romania;1. School of Geography, South China Normal University, Guangzhou 510631, China;2. Gannan Normal University, Ganzhou 341000, China;3. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xian 710061, China;1. Department of Bioenvironmental Systems Engineering, National Taiwan University, Taipei 106, Taiwan, ROC;2. Center for Weather Climate and Disaster Research, National Taiwan University, Taipei 106, Taiwan, ROC;3. Institute of Oceanography, National Taiwan University, Taipei 106, Taiwan, ROC;1. Laboratoire des Matériaux Utiles, Institut National de Recherche et d’Analyse Physico-chimiques, 2026 Technopole de Sidi Thabet, Tunisia;2. Université de Tunis El Manar, Département de Géologie, Faculté des Sciences de Tunis, 2092 El Manar, Tunis, Tunisia;3. School of Earth and Environmental Sciences, James Cook University, Townsville, Queensland, Australia;4. Stable Isotope Lab., Inst. of Mineralogy and Geochemistry, University of Lausanne, Lausanne, Switzerland;5. Department of Mineralogy, Petrology and Economic Geology, Sofia University, Sofia, Bulgaria |
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| Abstract: | In Douala (Littoral Cameroon), the Cretaceous to Quaternary formation composed of marine to continental sediments are covered by ferrallitic soils. These sediments and soils have high contents of SiO2 (≥70.0 wt%), intermediate contents of Al2O3 (11.6–28.4 wt%), Fe2O3 (0.00–20.5 wt%) and TiO2 (0.04–4.08 wt%), while K2O (≤0.18 wt%), Na2O (≤0.04 wt%), MgO (≤0.14 wt%) and CaO (≤0.02 wt%) are very low to extremely low. Apart from silica, major oxides and trace elements (REE included) are more concentrated in the fine fraction (<62.5 μm) whose proportions of phyllosilicates and heavy minerals are significant. The close co-associations between Zr, Hf, Th and ∑REE in this fraction suggest that REE distribution is controlled by monazite and zircon. CIA values indicate intense weathering. Weathering products are characterized by the association Al2O3 and Ga in kaolinite; the strong correlation between Fe2O3 and V in hematite and goethite; the affinity of TiO2 with HFSE (Hf, Nb, Th, Y and Zr) in heavy minerals. The ICV values suggest mature sediments. The PCI indicates a well-drained environment whereas U/Th and V/Cr ratios imply oxic conditions. La/Sc, La/Co, Th/Cr, Th/Sc and Eu/Eu* elemental ratios suggest a source with felsic components. Discrimination diagrams are consistent with the felsic source. The REE patterns of some High-K granite and granodiorite of the Congo Craton resemble those of the samples, indicating that they derive from similar source rocks. |
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| Keywords: | Littoral Cameroon Strata sediments Soils Geochemistry Weathering Source rocks |
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